The invention relates to a pipe fitting for connecting a first or branch pipe to a second or main pipe and to a method for connecting the first pipe to the second pipe by adhesively securing the fitting in place. More particularly, the invention concerns a T fitting having a saddle that is bonded to a main plastic pipe and then connected to a branch plastic pipe, thereby joining the pipes.
A T fitting is typically used to connect a first pipe, called herein the branch pipe, to a second or main pipe that continues past the point of connection. Ordinarily, the branch pipe has a smaller diameter and the fitting is referred to as a reduction T. For example, a horizontal water or sewage pipe often is connected into a larger vertical pipe, or "riser". With conventional T's, to join the pipes, the riser must be cut. If the riser is already installed, it must be cut twice in order to remove a section and make room for the reduction T. To assure a leakproof fit, the cuts should be substantially perpendicular to the longitudinal axis of the pipe and the ends formed by these cuts should extend well into enlarged collars on the fitting. Cutting an installed pipe is often very difficult due to the awkward location of the pipe, inside a wall, floor, a ceiling. Once an installed pipe is cut, the newly formed ends of the pipe must be bent away from each other to allow them to slip into the T fitting. Little or no axial movement of the ends is ordinarily possible.
Even in new construction, using conventional fittings, the exact floor-to-floor length of riser must be cut. The riser is installed, the fitting is located so that the branch pipe connection appears to extend in the correct direction, the next length of riser is fitted into the fitting and this process is repeated from floor to floor. This is time consuming and expensive. Moreover, once facilities have been completed, it can be found that the conventional T fitting is not appropriately directed and this "roughed-in" plumbing then must be pulled apart and reassembled properly, adding further to the time and expense.
To overcome some of the problems associated with conventional T fittings, somewhat different fittings have been suggested for use with plastic pipes. Several have stems to receive a branch pipe and mounting sections that clamp permanently about the main pipe. At least one proposed fitting for a plastic pipe has arms forming a saddle partially embracing a pipe into which an opening is to be made and to which another branch pipe is to be secured. This fitting is affixed to the plastic pipe by applying a fluid adhesive or solvent type bonding liquid. The solvent cures and bonds the fitting to the pipe. A hole is then drilled into the pipe through the fitting's central opening, and the branch pipe is connected.
The bonded in place fitting just described has a saddle inner diameter equal to the outside diameter of the pipe on which they are to be mounted. Arms extend more than 180.degree. around the perimeter of the pipe. The ends of these arms are spaced apart a distance less than the pipe O.D. Consequently, as such a fitting is located on the main pipe, the ends resiliently engage the pipe and slide into place. These arms can scrape a good portion of the solvent off of the pipe while the pipe wipes solvent from the sliding arm surfaces. An inadequate supply of solvent between the arms and the pipe can be the result. Only the resilience of the arms partially embracing the main pipe holds the fitting in place during setting of the adhesive and when the inside of the fitting and the outside of the pipe are brought together, pockets of air may be trapped between the surfaces of the fitting and the pipe resulting in unbonded areas. Manual coating of the pipe and fitting with adhesive very often can result in little or no adhesive at some point. Less than complete bonding of the contacting parts raises the possibility of leakage.
Prior suggestions for bonded-in-place fittings overlook the typical out-of-round condition of extruded pipe. While molded fittings with surfaces designed to fit the O.D. of a main pipe may have perfectly cylindrical surfaces for this purpose, extrusion of plastic pipe does not result in precision cylindrical outer pipe surfaces. The fitting and pipe surfaces therefor, can be expected to be far less than a perfect match. This also increases the likelihood of inadequate bonding. Extremely high bonding forces between the fitting and the pipe can overcome failure of the surfaces to properly mate, but such forces will not be provided by the snapped into place fitting in which only the resilience of the arms embracing the pipe hold the fitting in place.
Accordingly, a need exists for T fitting that overcomes not only the problems associated with conventional T fittings, but also the problems arising from the use of known bonded-in-place fittings for plastic pipes. More specifically, a T fitting is desirable that is simply and inexpensively manufactured and easily but securely attached.